She stepped into the limelight in 1986 by claiming the title of Miss Denmark when eighteen, allowing her to represent her country at the Miss Universe pageant. This provided an invaluable springboard to launch herself as an international model. She left her home to pursue modeling in Paris at the age of eighteen.

In 1991, she starred in the music video for Chris Isaak's song "Wicked Game". In the video, she is depicted as Isaak's lover. Christensen is topless for much of the video, though her nudity is relatively concealed with clever camera angles. It was decided that full frontal nudity would not be suitabile for mainstream release. Viewers still reacted to Christensen's sexually suggestive performance, and the video was later featured on MTV's 'Sexiest Video of All-Time'.

Helena has claimed on several occasions to be a cheese addict, admitting that "There've been times when I've bought a whole pound of cheese and walked down the street and eaten it in one go... I think it's incredibly sensual." British Cheese Board

Christensen declares that "Whenever my head is like a maze, I turn to the easy things in life, the things that mean the most to me: Sex and cheese. These things are connected. Truth be told, I love all cheese: French cheese, Italian cheese, even British cheese, but Danish cheese is the greatest. I get my best nightmares after I eat Danish cheese. Actually I've seriously thought about getting a cheese tattoo. A nice Edam on my shoulder, maybe."

Christensen is often considered to be one of the more popular supermodels of the 1990s. She has appeared on a slew on magazine covers and fashion campaigns. She was in the Victoria's Secret catalog and in their television commercials. She has an antiques shop in New York and sells some of her clothes in her mother's Yo-Yo Second Hand Shop in Christianshavn. She drives a Morris Minor car.

She has been romantically linked to the late singer of INXS, Michael Hutchence, Leonardo DiCaprio and Billy Corgan. She has one child, son Mingus Luchien Reedus born October 22, 1999 with former model Norman Reedus. Norman and Helena split in 2003.

Helena co-founded Nylon magazine and served as the creative director. She is no longer involved with the magazine.

On June 2006, Helena Christensen admitted to taking drugs. She says she smoked cannabis. Christensen said, "I wouldn’t say no if somebody passed me a joint.” The catwalk queen claims that models are attracted to the apparent glamour of Class A narcotics, but she didn't use them. She told Britain's Grazia magazine, "“It was never a problem for me. I was brought up with a lot of discipline so I wasn’t attracted to it. But there were a lot of young, beautiful girls on the party scene, with a lot of drugs around. I’m not a saint, but drugs were never my thing.”